linux-kernel - Re: [PATCH V1] oom: avoid selecting threads sharing mm with init

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Message-ID: <alpine.DEB.2.02.1309261143160.10904@chino.kir.corp.google.com>
Date:	Thu, 26 Sep 2013 11:44:13 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Ming Liu <ming.liu@...driver.com>
cc:	akpm@...ux-foundation.org, mhocko@...e.cz, rusty@...tcorp.com.au,
	hannes@...xchg.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V1] oom: avoid selecting threads sharing mm with init

On Thu, 26 Sep 2013, Ming Liu wrote:

> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 314e9d2..7e50a95 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -113,11 +113,22 @@ struct task_struct *find_lock_task_mm(struct task_struct *p)
>  static bool oom_unkillable_task(struct task_struct *p,
>  		const struct mem_cgroup *memcg, const nodemask_t *nodemask)
>  {
> +	struct task_struct *init_tsk;
> +
>  	if (is_global_init(p))
>  		return true;
>  	if (p->flags & PF_KTHREAD)
>  		return true;
>  
> +	/* It won't help free memory if p is sharing mm with init */
> +	rcu_read_lock();
> +	init_tsk = find_task_by_pid_ns(1, &init_pid_ns);
> +	if(p->mm == init_tsk->mm) {
> +		rcu_read_unlock();
> +		return true;
> +	}
> +	rcu_read_unlock();
> +
>  	/* When mem_cgroup_out_of_memory() and p is not member of the group */
>  	if (memcg && !task_in_mem_cgroup(p, memcg))
>  		return true;

You're aware of init_mm?

Can you post the kernel log when one of these "extreme cases" happens?
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